1. Duncan, D. R. The colour of pigment mixtures. J. Oil Colour Chem. Ass., 1949, 32, 296–321.
2. Nickerson, D. Spectrophotometric Data for a Collection of Munsell Samples. Washington, D. C: U.S. Department of Agriculture, 1957.
3. Pratt, L. S. The Chemistry and Physics of Organic Pigments. New York: Wiley, 1947. Pp. 305.
4. Simonds, J. L. Application of characteristic vector analysis to photographic and optical response data. J. Opt. Soc. Amer., 1963, 53, 968–974.